1. Field of the Invention
The present invention relates to a clutch state determining device for determining engagement or disengagement of a clutch, based on an engine rotation signal outputted by a rotation speed sensor, without using a shift operation switch such as a clutch switch or a neutral switch.
2. Description of Related Art
Usually, if gear-shifting operation is performed while a vehicle having a manual gearshift (a manual transmission) is traveling, an accelerator, which has been pressed, is released first, and then, a clutch pedal is pressed. A clutch switch is disposed near the clutch pedal for determining whether the clutch pedal is pressed to a predetermined position. For instance, the predetermined position is a position where the clutch pedal is pressed lightly. An engine control unit (ECU) determines that the clutch is in a disengaged state if an ON-signal is inputted from the clutch switch, and determines that the clutch is in an engaged state if an OFF-signal is inputted from the clutch switch. Then, the ECU outputs a control signal to the engine for performing a predetermined control. This technology is disclosed in Unexamined Japanese Patent Application Publication No. 2002-188658 (pages 1 to 12 and FIGS. 1 to 7) or No. 2002-266895 (pages 1 to 8 and FIGS. 1 to 3), for instance.
However, in the case where the engagement or the disengagement of the clutch is determined by using the clutch switch as in the above technology, the cost is increased because the switch equipment is used and the number of man-hours is increased because fine adjustment is necessary after the clutch switch is mounted. Moreover, detection accuracy is deteriorated by a change with time of the clutch. In the above technology, the clutch switch is set to determine that the clutch is disengaged even if the clutch pedal is pressed only slightly or by a play, or even if the clutch is brought to partial clutch engagement, for instance. Thus, determination accuracy of the engagement or the disengagement of the clutch is low.